Grid heat sink

ABSTRACT

A grid heat sink includes primary fins extending from a base and cross fins which intersect the primary fins and form a number of channels. A fan moves cooling air through the channels to remove heat from the primary and cross fins. In one illustrative embodiment, the grid heat sink includes a base, a plurality of intersecting fins, and a plurality of channels formed by the intersecting fins. Each of the channels accept cooling air at an input side of the grid heat sink and direct the cooling air to exit an output side of the grid heat sink.

BACKGROUND

As an electronic component operates, the electron flow within thecomponent generates heat. If this heat is not removed, the electroniccomponent may overheat, causing malfunction or damage to the component.The heat generated by the electronic component can be dissipated in anumber of ways, including using a heat sink which absorbs and dissipatesthe heat via direct air convection.

Improvements in integrated circuit design and fabrication techniques areallowing IC manufacturers to produce smaller IC devices and otherelectronic components which operate at increasingly faster speeds andwhich perform an increasingly higher number of operations. As theoperating speed of an electronic component increases, so too does theheat generated by these components. Further, computer components arebeing more densely packaged. These factors contribute to the desire fora heat sink which has more thermal and volumetric efficiency in removingheat from these electronic components.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of theprinciples described herein and are a part of the specification. Theillustrated embodiments are merely examples and do not limit the scopeof the claims.

FIG. 1 is a perspective view of an illustrative heat sink, according toone embodiment of principles described herein.

FIG. 2 is a perspective view of an illustrative heat sink, according toone embodiment of principles described herein.

FIGS. 3A and 3B are diagrams of an illustrative cooling system,according to one embodiment of principles described herein.

FIG. 4 is a perspective view of an illustrative grid heat sink accordingto one embodiment of principles described herein.

FIG. 5A is an illustrative diagram of a temperature profile within afinned heat sink, according to one embodiment of principles describedherein.

FIG. 5B is an illustrative diagram of a temperature profile within agrid heat sink, according to one embodiment of principles describedherein.

FIG. 6A is an illustrative graph of heat removal as a function of airflux, according to one embodiment of principles described herein.

FIG. 6B is an illustrative graph of a difference between heat sinksurface temperature and air exit temperature as a function of air flux,according to one embodiment of principles described herein.

FIG. 7 is a front view of an illustrative grid heat sink, according toone embodiment of principles described herein.

FIG. 8 is a front view of an illustrative grid heat sink, according toone embodiment of principles described herein.

FIG. 9 is a front view of an illustrative grid heat sink, according toone embodiment of principles described herein.

FIG. 10 is a cross-sectional view of an illustrative grid heat sink,according to one embodiment of principles described herein.

FIG. 11 is a front view of an illustrative grid heat sink, according toone illustrative embodiment of principles described herein.

FIG. 12 is a front view of an illustrative grid heat sink, according toone embodiment of principles described herein.

FIGS. 13A-D show illustrative steps in forming a grid heat sink from acontinuous sheet of thermally conductive material, according to oneembodiment of principles described herein.

FIG. 14 is a cross-sectional view of an illustrative grid heat sinkformed with a continuous sheet of thermally conductive material,according to one embodiment of principles described herein.

FIG. 15 is a cross-sectional view of an illustrative grid heat sinkformed with a continuous sheet of thermally conductive material,according to one embodiment of principles described herein.

FIG. 16 is a diagram of an illustrative cooling system whichincorporates a grid heat sink, according to one embodiment of principlesdescribed herein.

FIG. 17 is a diagram of an illustrative cooling system whichincorporates a grid heat sink, according to one embodiment of principlesdescribed herein.

FIG. 18 is a diagram of an illustrative cooling system incorporated intoa blade server, according to one embodiment of principles describedherein.

FIG. 19 is a diagram of an illustrative computer rack containing anumber of blade servers, according to one embodiment of principlesdescribed herein.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

As an electronic component operates, the electron flow within thecomponent generates heat. If this heat is not removed the electroniccomponent may overheat, causing malfunction or damage to the component.The heat generated by the electronic component can be dissipated in anumber of ways, including using a heat sink which absorbs and dissipatesthe heat via direct air convection.

Improvements in integrated circuit design and fabrication techniques areallowing IC manufacturers to produce smaller IC devices and otherelectronic components which operate at increasingly faster speeds andwhich perform an increasingly higher number of operations. As theoperating speed of an electronic component increases, so too does theheat generated by these components.

Additionally, computer components are being more densely packaged whichcan demand more thermal and volumetric efficiency in the heat removalsystems. For example, the shrinking sizes and increased functionality ofmodern electronic devices can result in much more restricted volumes forheat removal systems. In some computing architectures, such as arrays ofblade servers, these volume restricted computing devices may be placedin close proximity to each other.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present systems and methods. It will be apparent,however, to one skilled in the art that the present apparatus, systemsand methods may be practiced without these specific details. Referencein the specification to “an embodiment,” “an example” or similarlanguage means that a particular feature, structure, or characteristicdescribed in connection with the embodiment or example is included in atleast that one embodiment, but not necessarily in other embodiments. Thevarious instances of the phrase “in one embodiment” or similar phrasesin various places in the specification are not necessarily all referringto the same embodiment.

FIG. 1 is a perspective view of an illustrative heat sink (100) which isin thermal contact with underlying computer chip (115). The heat sink(100) includes a base (110) and a number of vertical fins (105). Airpasses through the vertical fins (105) and removes heat from the heatsink (100). The air may be moved by natural convention or forcedconvection. Natural convention utilizes the buoyancy forces of hot airto lift the heated air away from the fins and draw cool air into theheat sink to replace it. In forced convection cooling systems, a fan orother device creates a pressure difference or moving air flow which ischanneled through the fins. Natural conventions systems typically havemuch lower cooling capacities than forced convention cooling systems.

FIG. 2 is an illustrative diagram of heat sink (100) through which anair flow (200) passes. According to one illustrative embodiment, theheat sink (100) includes a base (110) with a thickness “d”. The heatsink (100) has a number of vertical fins (105) and an overall width “b”and length “L.” The air flow (200) passes through the fins (105)parallel to the plane of the base.

FIG. 3A is an illustrative diagram of a forced air cooling system (300)which includes a fan (305). The heat from the chip (115 ) is transferredinto the base (110) which distributes the heat into the vertical fins(105). The fan (305) may blow air stream directly into the vertical fins(105) in a process called impingement cooling. Alternatively, the fan(305) may create suction by removing air between the fins and blowing itout the top of the fan. A suction cooling system has inherentlimitations in the amount of pressure differential which can begenerated by the fan or blower.

FIG. 3B is an illustrative diagram of impingement cooling by the fan(305). Cooling air (310) is forced from above the fan (305) into theheat sink (100). A number of inefficiencies can arise in thisconfiguration. First, the distribution of the air over the heat sinksurfaces is not uniform. For example, the fan blade velocities arehighest at the perimeter of the fan. Consequently, higher pressures andair flow are generated at the perimeter of the fan. In the center of thefan, much lower air flow may occur. The air flow may recirculate beneaththe fan. Consequently, the center of the heat sink may not beeffectively cooled.

Additionally, heated air may be recirculated. For example, air from theheat sink may escape upwards, curve around the housing of the fan (305)and be sucked back into the fan (305). This recirculation may be avoidedby having a taller duct which encloses the fan. However, a taller ductmakes the already tall cooling assembly even taller. Further, even ifthe heated air is not recirculated, air which prematurely exits the heatsink is not utilized to its full capacity and reduces the overallcooling efficiency of the heat sink for a given air flow rate.

The amount of cooling provided by a heat sink depends on a number offactors. These factors may include: the temperature difference betweenthe cooling air and the surface of the heat sink, the volume of airforced through the heat sink, and the surface area of the heat sink.

FIG. 4 is a perspective view of one illustrative embodiment of a gridheat sink (400) which has significantly greater surface area thansimilarly sized finned heat sink (300). According to one illustrativeembodiment, the grid heat sink (400) includes base (420) with a numberof vertical fins (410). Horizontal fins (415) intersect the verticalfins (410) to form a grid with a number of channels (405). The channelsmay have a variety of geometries including, but not limited to, square,rectangle, hexagonal, or other geometries. In some illustrativeembodiments, the channels may extend through the heat sink and maintaina fairly constant cross-section. In other illustrative embodiments,cross sections of the channels (405) may vary from channel to channel orvary along the length of an individual channel.

FIG. 5A is a cross-sectional diagram of a finned heat sink (100) whichshows the temperature profile (500) in a space between the fins. Forpurposes of illustration, only one segment of the finned heat sink (100)is shown and the entire view has been rotated to so that the verticalfins (105) are horizontal. The temperature profile has three segments, afirst segment labeled T_(m) which represents the temperature through theconductive base (110). Surface temperature, T_(s), represents thetemperature of the surface of the heat sink at a given point. T(x)represents the air temperature profile through the open space betweenthe fins (105).

A heat flux, Q, moves from the underlying chip into the base. Thisraises the temperature of the base (110). As shown in FIG. 5A, there isslight decline in temperature profile T_(m) as the heat flux movesthrough the relatively high thermal conductivity base material. The airflow interacts with the surface of the heat sink (100) at the surfacetemperature (T_(s)). The temperature profile, T(x), through the air flowis illustrated as declining along the length of the profile. Themeasurement locations used to generate the temperature profile T(x) aremade along the centerline of the (505) of the heat sink segment. Theheight of the temperature profile is higher or lower than the centerline(505) to show the relative temperature differences through thetemperature profile. Ideally, the air temperature would be equal to thesurface temperature T_(s). This would result in a higher thermalefficiency of the heat sink in removing heat from the underlying chip.For laminar air flows, the air layers which travel near the surface ofthe heat sink are closer to the surface temperature T_(s), while layersthat are farther away from the surface may be at much lowertemperatures. For higher air flux rates, a turbulent flow may develop.In a turbulent flow, a much higher amount of mixing occurs in the air,which results in a more uniform temperature distribution and moreefficient heat transfer away from the heat sink.

FIG. 5B is a diagram of an illustrative section of a grid heat sink(400). As described above, a temperature flux Q enters the base (420)and is conducted up the primary fins (410) and into the cross fins(415). As an air flux passes through the grid heat sink (400), atemperature profile forms. The temperatures are measured along thecenterline (510). Through the thickness d of the base (420) there isslight decline in temperature. The additional surface area provided bythe cross fins (415) creates channels (405) with a characteristicdimension a and additional surface area. The temperature profile T(x)shows less severe declines and generates higher thermal efficiencies inremoving heat from the chip because there is a more uniform heating ofthe cooling air. Further, the enclosed channel prevents the prematureescape and recirculation problems of the air flow.

The grid heat sink allows for a much larger amount of heat removal forthe same size of heat sink and the same air flow rate, or the same heatremoval for a smaller coolant flow. Consequently, for a given system agrid heat sink may be smaller, thereby reducing the overall volume ofthe system. Additionally or alternatively, the increased thermalperformance may allow for lower operating temperatures of the heatgenerating component. The heat removal of various heat sinks as afunction of air flux can be estimated using Eq. 1.

$\begin{matrix}{{W(j)} = {0.023{mAb}\; \rho \; C\frac{{v(j)}{L(j)}}{\left( {d + a} \right)}{\left( \frac{\rho \; {{dv}(j)}}{\mu} \right)^{- 0.2}\left\lbrack {1 - {\exp \left( \frac{- L_{o}}{L(j)} \right)}} \right\rbrack}\left( {\Theta - T} \right)}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

Where:

W=heat removed from system in Watts

j=volume flow rate of air through the system

v=velocity of air

p=density of air

C=specific heat of air

μ=Newtonian viscosity of air

b=width of heat sink

L=length of heat sink

d=thickness of heat sink base

a=dimension of channel

θ=exit temperature of air

T=surface temperature of heat sink

m=2 for the fin cooling system and m≈4 for the grid system

FIG. 6A is an illustrative graph of the heat removed for a fin systemand a grid system as estimated by Eq. 1. The vertical axis representsheat removed in units of Watts from the heat sink by the passage ofcooling air. The horizontal axis is air flux through the heat sink incubic meters per second. The dashed line represents the heat removed ina grid system and the dash-dot line represents the heat removed from afin system. As can be seen from the graph, a grid system with comparablesize and mass removes significantly more heat than a fin system. Forexample, at 0.0075 cubic meters of air per second, the fin systemremoved approximately 45 Watts of heat. The grid system removedapproximately 85 Watts of heat.

A measure of the thermal efficiency of the heat sink is the differencebetween the exit temperature of the air (θ) and the surface temperatureof the heat sink (T). Ideally, the exit air temperature (θ) would beequal to the surface temperature of the heat sink (T). When the exit airtemperature equals the surface temperature of the heat sink, the air hasabsorbed all of the heat possible. To accomplish this level of thermalefficiency is often impractical because the size of the heat sinkbecomes infinitely larger. However, when comparing two heat sinks ofsimilar size, the thermal efficiency can provide a measure of theefficiency of the heat sink designs.

The difference (ΔT) between the exit air temperature (θ) and the surfacetemperature of the heat sink (T) can be estimated using the Eq. 2, shownbelow.

$\begin{matrix}{{{\Delta \; T} \equiv \left( {\Theta - T} \right)} = {W\left\lbrack {{{AbL}(j)}{\frac{{mh}(j)}{d + a}\left\lbrack {1 - {\exp \left( {- \frac{L_{o}}{L(j)}} \right)}} \right\rbrack}\left( {\Theta - T} \right)} \right\rbrack}^{- 1}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

FIG. 6B shows an illustrative graph of the results of Eq. 2 for a gridsystem and a fin system of comparable size. The horizontal axisrepresents the air flow rate through the heat sinks in cubic meters persecond. The temperature difference in degrees Celsius is shown along thevertical axis, with lower temperature differences at the bottom of theaxis and higher temperature differences shown proportionally higher onthe axis.

The temperature difference between the exit air and the heat sinksurface for the grid system is shown as a dotted line. The temperaturedifference for the fin system is shown as a dot-dashed line. As can beseen from the curves on the chart, the temperature differences becomesmaller for higher volume flow rates. There are a number of factorswhich could produce this result including increased turbulence in highervelocity flows. In general, turbulent flows are more efficient intransporting heat away from a surface than more ordered flows.Consequently as turbulence increases, the efficiency of the heat sinkcan increase.

The grid system has lower temperature differences than the fin systemfor all flow rates shown in FIG. 6B. For example, at a flow rate of0.0075 cubic meters per second, the temperature difference for the finsystem is approximately 6.5 degrees Celsius and the temperaturedifference for the grid system is approximately 3 degrees Celsius.Consequently, for a given flux of air through the heat sink, the gridsystem can be more efficient than the fin system in removing heat.

The grid heat sink could have a variety of configurations andgeometries. FIG. 7 shows a grid heat sink (700) which is in thermalcontact with an underlying chip (725). The grid heat sink (700) includesa base (720) which distributes heat to the various vertical fins (710).These primary vertical fins (710) serve as conduction paths to theoverlying structures. According to one illustrative embodiment, a numberof cross fins (715) intersect the primary vertical fins (710) andprovide additional surface area and structural support for the heat sink(700). As discussed above, the intersecting fins create a number ofchannels (730). Air flow is directed through the channels to provide thedesired cooling of the heat sink (700) and underlying chip (725). Thesechannels may have a substantially uniform cross-section through thelength of the heat sink (700). Additionally or alternatively, there maybe various disruptions in the channels, such as surface roughness,offsets of the channel cross-section, etc. These obstructions maygenerate additional focused cooling by direct impingement of the flow onthe obstruction or may serve to create additional turbulent flow withinthe channel to improve heat transfer. In some embodiments, the crosssection of the channels may increase toward the exit to allow forexpansion of the air flow. The volume and temperature of the expandingair flow are physically related such that an expansion of the volume ofthe air flow results in a lower temperature within the air flow.Consequently, altering the cross-section of the channel may be used tomake adjustments to the temperature of the air.

FIG. 8 is a diagram of an illustrative heat sink (800) which has taperedprimary fins (810). As discussed above, the primary fins (810) serve asa conduction path for the majority of the heat which is dissipated inthe rest of the structure. By making the base of the primary fins (810)thicker at the base where there is a greater amount of heat flux, theheat sink temperature can be more uniform.

According to one embodiment, the cross fins (815) may be significantlythinner than the primary fins (810). The cross fins (815) need onlyconduct a relatively small amount of heat from the adjoining primaryfins through the cross fin area. Consequently, the cross fins could berelatively thin with little performance degradation. Increasing thethickness of the fins results in a reduction of the cross area of theair channels (830). A quantitative trade off between fin geometry andair flow can be performed for specific designs, heat loads, and fancombinations.

Further, the cross-section of the channels (830) may vary along throughthe height of the heat sink (820). For example, if high volume flowrates are desired near the base (820) of the heat sink (800), the crosssectional area of the channels at the base could be increased.Alternatively, if high surface areas are desired at the base, aplurality of smaller channels could be formed near the base (820).

According to one illustrative embodiment, the grid heat sink may beformed by joining a number of stacked tubes. The tubes may be made froma thermally conductive material such as metal and joined using anynumber of techniques. For example, the tubes may be joined usingwelding, soldering, adhesive, or other techniques. The tubes may havevarious cross-sectional geometries which may vary from tube to tubeand/or along the length of the individual tubes.

FIG. 9 is a diagram of one illustrative embodiment of a grid heat sink(900). The grid heat sink (900) includes a number of radial primary fins(910) which extend from a base (920). The base (920) is in directthermal contact with a chip (925). The heat flux into the base (920) isconcentrated in the center of the base directly over the chip (925). Theradial primary fins arms (910) connected to the center of the base (920)to more directly conduct the heat from the base (920). A number ofcurved cross fins (915) intersect the radial primary fins (910) to forma number of channels (930). The channels (930) can be of any suitablegeometry including triangular, rectangular, wedge shaped, or any othersuitable geometry.

FIG. 10 is a cross-sectional diagram of an illustrative heat sink (1000)which includes a number of primary fins (1010) which extend from a base(1020). The base (1020) is in thermal contact with an underlying chip(1025). The cross fins (1015) extend from the primary fins (1010) but donot intersect the adjacent primary fins. The result is a number of openchannels (1030) between the primary fins. The extension of the crossfins (1015) into the open channels (1030) create a high surface areawithin the channels. In some embodiments, higher pressure fluid flow maybe applied to one portion of a heat sink than other portions of the heatsink. For example, in the embodiment shown in FIG. 10, a higher pressurefluid flow may be applied to the lower portion of the open channel(1030) near the base. This could result in a two dimensional fluid flow,with a portion of the fluid passing axially down the open channel and aportion of the fluid passing through the serpentine upper portion of thechannel to exit through the top of the heat sink (1000).

According to one illustrative embodiment, the grid heat sink may alsohave a number of external fins (1035) which extend beyond the interiorgrid structure to provide additional cooling by external force or freeconvention.

FIG. 11 is a diagram of an illustrative heat sink (1100) which includesa base (1120) which is in thermal contact with an underlying chip(1125). A number of primary fins (1110) extend upward from the base(1120). The primary fins (1110) and base (1120) can be formed usingmetal extrusion processes. The channels (1145) can be created byinserting bent sheet metal forms (1115, 1130, 1135) into the spacesbetween the primary fins (1110). The shape of the sheet metal formdetermines the size, number and geometry of the resulting channels(1145). For example, a first form (1115) has relatively large channels.The second form (1130) creates smaller and more numerous channels.Consequently the second form (1130) creates more surface area within theheat sink (1100). A third form (1135) creates smaller channels closer tothe base (1120) and larger channels near the lid (1140).

The sheet metal forms (1115, 1130, 1135) may be thermally andstructurally joined to the primary fins (1110) in a number of ways,including, but not limited to welding, soldering, adhesives, or springforces. For example, the lid (1140) could compress the sheet metal formsbetween the primary fins (1110) and produce appropriate thermal contactbetween the forms (1115, 1130, 1135) and the primary fins (1110) andbase (1120).

FIG. 12 is an illustrative diagram of a heat sink (1200) whichincorporates a continuous thermally conductive sheet (1215) which isbent to form channels (1230). The conductive sheet (1215) is placed overthe primary fins (1210) and contacts the base (1220). A cover (1205)encloses upper portion of the heat sink (1200) and forms some of thesurfaces of the channels (1230).

FIGS. 13A-13D are illustrations which show steps in forming a grid heatsink (1300) from a continuous sheet of conductive material (1305).According to one illustrative embodiment, two bends (1315, 1310) aremade in the sheet (1305) to create a U shaped geometry as shown in FIG.13A. FIG. 13B illustrates additional bends (1325, 1320) being made inthe sheet to form a first channel (1330). As shown in FIG. 13C, thisprocess is repeated to form a column which includes two additionalchannels (1335, 1340). FIG. 13D illustrates the formation of additionalcolumns to form a grid which is attached to a base (1345). As discussedabove, a variety of methods may be used to attach the grid to the baseor make internal joints in the grid. The resulting grid heat sink (1300)is formed from a continuous sheet of conductive material (1305) and abase (1345). The type, thickness, and other properties of the conductivematerial (1305) can be altered according to the specific design needs.

FIG. 14 is a diagram of an alternative geometry for forming a grid heatsink (1400) from a continuous sheet of thermally conductive material(1401). According to one illustrative embodiment, the thermallyconductive material (1401) is bent and joined at various contact points(1415) to form channels (1405). The entire grid structure is joined to abase structure (1415).

FIG. 15 is a diagram of an alternative geometry for forming a grid heatsink (1500) from a continuous sheet of thermally conductive material(1510). According to one illustrative embodiment, the thermallyconductive material (1510) is bent and joined to form relatively openchannels (1505). The entire grid structure is joined to a base structure(1515).

FIG. 16 is a diagram of an illustrative cooling system (1600) for a chip(1615). The air flow (1605) is directed through two ducted fans (1620),into a manifold (1620), and then through a grid heat sink (1625). Thegrid heat sink (1625) is thermally connected to the chip (1615) andconducts heat away from the chip (1615). The air flow (1605) removes theheat from the grid heat sink (1625) by convective heat transfer. In thisillustrative embodiment, the ducted fans (1610) are used to create ahigh air pressure in the manifold (1620) which forces the air throughthe channels in the grid heat sink (1625). This approach may have anumber of advantages for over suction systems where the fan creates lowpressure to suck air through a heat sink. The suction action of the fanis limited in the pressure differential which can be generated. Asuction fan system can not produce a pressure any lower than zero.Consequently, the maximum pressure differential which can be produced bya suction fan system is equal to the supply pressure, which is typicallyatmospheric pressure. In contrast, fan systems which create highpressure at the inlet to force air through a heat sink do not have asimilar limitation in the maximum pressure which can be generated.Rather, pressure systems are limited only by the mechanics of thecooling system, such as the design of the fans, the available power, thephysical strength of the fans, manifold and grid heat sink, etc.Consequently, a pressure system could produce several atmospheres ofpressure to drive the air flow through the grid heat sink. This could beparticularly advantageous when very small channels are used in the gridheat sink.

FIG. 17 shows an illustrative embodiment of the a cooling system (1700)which includes a blower fan (1710) which attached to a manifold (1720)which directs the air flow through a grid heat sink (1725). The gridheat sink (1725) is used to cool an underlying chip (1715).

FIG. 18 is a side view of an illustrative cooling system (1700) within ablade server (1800) which is represented by a dotted outline. Bladeservers (1800) are very compact computers which may have one or morecentral processor units (CPUs) (1805). The grid heat sink (1725) isthermally connected to the CPU (1805). An air flow (1810) is generatedby the fan (1710). The air flow (1810) through openings in the left ofthe blade server (1800) and enters the fan (1710) where it is compressedand ejected into the manifold (1720). The manifold (1720) directs theair flow (1810) through the grid heat sink (1725). The air flow (1810)is then vented out of the right of the blade server (1800).

The compact design, low profile and thermal efficiency may make the gridcooling system particularly suitable for applications which havegeometric constraints. FIG. 19 is front view of an illustrative rack(1900) of blade servers (1800). The rack (1900) contains 16 bladeservers (1800), each of which may have multiple processors. The front ofeach of the blade servers (1800) has a number of openings throughcooling air is drawn. After passing over the various components withinthe blade server (1800), the heated air is vented out the back of therack. A variety of fan configurations can be used. According to oneillustrative embodiment, one larger fan or array of fans supplypressurized air for multiple grid heat sinks.

In sum, a grid heat sink provides increased thermal and volumetricefficiency when compared to fin heat sinks. The channels formed by theprimary fins and cross fins provide additional surface area and preventthe premature exit and recirculation of cooling air. Consequently, gridheat sinks may be particularly desirable for more compact systems whichhave concentrated heat sources.

The preceding description has been presented only to illustrate anddescribe embodiments and examples of the principles described. Thisdescription is not intended to be exhaustive or to limit theseprinciples to any precise form disclosed. Many modifications andvariations are possible in light of the above teaching.

1. A grid heat sink comprises: a plurality of primary fins extendingfrom a base; a plurality of cross fins configured to intersect saidprimary fins to form a grid, said grid having a plurality of channelsbeing configured to extend from a first side to a second side of saidgrid heat sink; and a fan, said fan being configured to move cooling airthrough said plurality of channels, said cooling air removing heat fromsaid plurality of primary fins and said plurality of cross fins.
 2. Thegrid heat sink of claim 1, in which said primary fins comprise a taperedcross-section.
 3. The grid heat sink of claim 1, further comprising aformed sheet of conductive material configured to be placed between saidprimary fins to said plurality of channels.
 4. The grid heat sink ofclaim 1, further comprising a top plate, said top plate being configuredto be attached between said distal ends of said primary fins.
 5. Thegrid heat sink of claim 1, in which said fan is a blower fan, saidblower fan being configured to pressurize said cooling air and directsaid pressurized cooling air into said channels.
 6. The grid heat sinkof claim 1, in which said primary fins and cross fins are constructedfrom a continuous sheet of thermally conductive material.
 7. The gridheat sink of claim 6, further comprising welded joints, said weldedjoints joining a first section of said continuous sheet of thermallyconductive material to a second section of said continuous sheet ofthermally conductive material.
 8. The grid heat sink of claim 1, inwhich said grid heat sink comprises: an extruded base and primary fins;and a sheet metal cross fins.
 9. The grid heat sink of claim 1, in whichsaid grid heat sink comprises at least one of: a cast metal, a compositematerial, and a metal injection molded material.
 10. The grid heat sinkof claim 1, in which cooling air entering a first channel does not mixwith cooling air entering a second channel until said cooling air exitssaid grid heat sink.
 11. The grid heat sink of claim 10, in which saidfan is configured to create cooling air with a positive pressure, saidpositive pressure varying substantially over an inlet side of said gridheat sink.
 12. The grid heat sink of claim 1, in which said channelshave varying cross-sectional geometries.
 13. A grid heat sink comprises:a base; a plurality of intersecting fins; a plurality of channels formedby said intersecting fins, each of said channels being configured toaccept cooling air at an input side of said grid heat sink and directsaid cooling air to exit an output side of said grid heat sink.
 14. Thegrid heat sink of claim 13, further comprising a chip, said chip beingin thermal contact with said base and generating thermal heat, saidthermal heat being conducted through said base to said plurality ofintersecting fins, said cooling air being configured pass through saidplurality of channels and to remove said thermal heat from saidintersecting fins.
 15. The grid heat sink of claim 13, in which each ofsaid plurality of channels is enclosed on four sides by saidintersecting fins, each of said channels being mutually parallel to eachother and being parallel to said base.